The broad, long term objective of this research is to determine the clinical utility, if any, of spontaneous eye blinking (SEB) in human infants. Previous work has established that (a) average baseline rates of SEB are altered under some pathological conditions, (b) central dopamine systems participate in the regulation of SEB rate, (c) modest evidence of developmental continuity of SEB mechanisms exists, and (d) the rate of SEB can be altered temporarily in adults, children and infants. Previous work from these and other disciplines provides a strong empirical foundation for initiating research with human infants. Specific aims of the current project are: (1) Describe individual differences in features of SEB and assess the stability of individual differences in the second half of the first year. (2) Test whether individual differences in SEB rate are linked to variation in infant temperament and whether transient rate changes are linked to changes in motor activation. (3) Attempt to alter the rate of spontaneous blinking by presenting stimuli predicted to increase or decrease SEB rate. Achieving these Aims will help clarify the development, mechanisms and functional relationships of SEB and lay the groundwork for an investigation into potential clinical utility of SEB in infants. To meet these Aims, a longitudinal study is proposed. At 4 and 12 months of age, infants will be presented with stimuli while several measurements are taken. Measurements include: digital video recordings of infants' eyes (to record blinks), heart rate and variability, motor activity, and two assessments of temperament (the Infant Behavior Questionnaire-Revised and a laboratory assessment). The results will provide for the first time, longitudinal data on features of SEB in human infants. Moreover, by determining whether variations in SEB between individuals might be meaningful for other behavioral systems such as temperament, we would gain potentially useful information on whether individual differences in SEB rate may, in the future, predict behavioral and health-related outcomes. [unreadable] [unreadable]